Fetal urethral abnormalities manifesting as lower urinary tract obstruction (“LUTO”) are associated with significant morbidity and mortality. This sporadic condition occurs in approximately 1:5000-8000 male fetuses with the most common cause being posterior valves. In females, urethral atresia accounts for the majority of cases. Untreated, LUTO may lead to hydronephrosis, renal dysplasia, and perinatal death in up to 90% of patients. Prenatally diagnosed cases of posterior urethral valves have a 30-50% mortality. If oligohydramnios is present at the time of prenatal diagnosis, the mortality is as high as 77%. Death is attributed to pulmonary hypoplasia and renal dysplasia. To avert these complications, percutaneous vesicoamniotic shunts or open fetal vesicostomy have been previously performed in utero to treat these conditions.
Percutaneous ultrasound-guided vesicoamniotic shunting (“VAS”) of fetuses with LUTO was first reported in the early 1980's. The goal of therapy is to avert pulmonary hypoplasia from the attendant oligohydramnios as well as to preserve renal function. Fetal vesicostomy via open fetal surgery was at one time proposed as a way to avoid the limitations of VAS, but did not gain acceptance and is thus only of historical interest. VAS is currently being offered only to patients without sonographic or biochemical evidence consistent with renal cystic dysplasia, normal karyotype, and lack of associated major congenital anomalies.
Despite adequate placement, malfunction of VAS may occur up to 60% of the time. The shunt may pull from the skin into the fetal abdomen, resulting in iatrogenic ascites, or out of the fetal bladder, with no further derivation of urine. The shunt may pull out of the fetus altogether as well. Replacement of the shunt is associated with an additive risk of fetal demise, chorioamnionitis, premature rupture of membranes and miscarriage or preterm delivery, for a total perinatal loss rate of approximately 4% per instance.
In 1995, endoscopy was introduced in the management of fetuses with LUTO. Endoscopy provided a new set of possibilities in these cases, including cystoscopy, ablation of posterior urethral valves, lysis of obstructive ureteroceles, fetal hydrolaparoscopy and fetal cystotomy, and endoscopic documentation of vesicoamniotic shunt placement. Results showed, however, that the differential diagnosis of type III posterior urethral valves and urethral atresia was very difficult or impossible to make, and that ablation of the valves could be technically challenging and inaccurate at times.
As a specific example of prior treatments, FIG. 9 is an ultrasound showing use of a conventional shunt, resulting in urinary ascites secondary to a dislodged shunt (indicated as ‘S’) in the fetal bladder (indicated as ‘B’) of a patient. Anhydramnios is also visible. Another specific example of a prior treatment is depicted in FIG. 10, which is a fetal hydrolaparoscopy image showing a prior art shunt which has embedded in the fetal bladder (indicated as ‘B’).
In view of the above, it is desirable to provide an effective medical device, system and method of fetal shunting for patients with fetal lower urinary tract obstruction.